1. Field of the Invention
This invention relates generally to electrical contacts for housings and more particularly to contact members for providing electrical connection between components such as doors, panels, frameworks etc. of housings for electrical or electronic equipment for example.
2. Description of the Related Art
Devices for electrically interconnecting components of a housing, for example to ensure that the housing provides proper shielding against transmission of electromagnetic radiation into or out of the housing, are well known. Such contact devices may be used to provide connections between panels of the housing or between panels and the framework, and also between doors and adjacent panels or frame elements. These contacts can be provided in the form of a elongate strip which can be mounted on a flange of one housing component and makes contact with an adjacent component to provide the required electrical connection between the components.
One such known contact device is illustrated in FIG. 1 of the drawings. FIG. 1 is a schematic cross-section through part of a door frame 1 of a housing for receiving the edge of a door 2 when the door is closed. The contact strip 3, also shown in cross-section, is mounted on a flange 4 of the door frame 1. The illustrated section of the contact strip 3 comprises a spring clip indicated generally at 5 for mounting the contact strip over the edge 6 of the flange 4. The spring clip 5 has a front clip portion 7 and a rear clip portion 8 which grip the flange 4 to hold the contact strip in place. A spring leaf 9 extends away from the spring clip 5 at an acute angle to the flange 4 and is bent, at bend 10, so as to extend back towards the flange 4 where the inwardly-turned, free end 11 of the spring leaf contacts the surface of the flange. The contact device 3 is formed as an elongate strip, extending over the height of the flange 4 in a direction perpendicular to the plane of the page. The contact strip is divided into individual contact members, each consisting of a spring clip and spring leaf, adjacent contact members being integrally connected side by side by a bridging portion. The front portion 7 of each spring clip 5 can be pressed from the material of the spring leaf 9 at periodic intervals along the length of the strip, whereby the complete contact strip can be formed by pressing and shaping a strip of sheet metal.
A rubber gasket 12 is mounted in the channel defined by the door frame 1 and provides a resilient stop for the door 2 when the door is fully closed. As the door closes in the direction of the arrow A in the figure, the edge of the door first contacts the spring leaf 9 at a point P. As the door continues to close, the edge of the door presses against spring leaf 9 compressing the leaf towards the flange 4. As the spring leaf 9 is compressed, the free end 11 of the spring leaf rides along flange 4 until the fully closed position, shown by the broken lines in the figure, is achieved.
It will be seen that in this process the free end 11 of the spring leaf 9 moves a distance X as the edge of the door 2 moves a distance Y from first contact point P to the final stop position at gasket 12. Since clearance must be provided for the forward travel X of spring leaf 9, the required distance of forward travel Y is relatively large. In particular, considering the door latching mechanism, only a limited amount of forward travel of the door 2 can be obtained from a 90.degree. turn of a door handle, and this is often less than the required distance Y. The result is that after turning the handle to obtain a certain degree of forward movement, the door must be manually pushed through the remaining distance so that the edge of the door abuts the gasket 12 and the door is properly latched.
Another known contact strip is disclosed in GB-A-2254490. This contact strip provides for electrical connection of adjacent webs of front panels of a modular housing. The strip comprises a series of contact members each having a spring clip and spring leaf similar to the contact strip 3 of FIG. 1. In this case, however, (using the equivalent reference numerals of FIG. 1 for reference) the spring leaf 9 is bent at 10 to form an abutment strip which extends generally perpendicular to the flange (or web) 4. In this case, therefore, as the spring leaf is compressed towards the flange 4, the edge of the abutment strip on the spring leaf serves as a stop to abut the surface of flange 4 and limit the compressive movement of the spring leaf relative to the flange.